This invention relates to a diamond tool used in a field where the generation of vibrations has to be avoided during processing as well as in a field where thermal resistance is required, and to a method for producing the same.
There have existed a variety of diamond tools which utilize the abrasion resistance of diamond, such as diamond bite, diamond dressers, diamond wire drawing dies, diamond surgical knives, etc.
These tools are generally formed by bonding a diamond chip to a shank of metal, such as stainless steel, by a powder metallurgical or active metal method or the like.
However, the above-mentioned tools formed by conventional bonding techniques suffer such problems as follows:
For example, in the case of machining a soft material, such as aluminum, brass, and oxygen-free copper, processing with precision cannot be achieved because of vibrations of the tool generated during processing. To solve this problem, the shank may be composed of highly rigid ceramics. At present, however, no appropriate technique has been established for bonding a diamond chip to a ceramic shank through a junction having similarly high rigidity. It has therefore been difficult to produce a diamond tool having a shank composed of highly rigid ceramics.
Also, for use under high temperature conditions, for example, from 1300.degree. C. to 1400.degree. C., because the thermal resistance of a shank itself and that of a junction between the shank and diamond are insufficient, the precision of processing a workpiece cannot be assured, or the tool cannot at all be used. For improving thermal resistance, it is possible to produce a shank from ceramics having thermal resistance, but as described above no suitable technique for bonding diamond with a ceramic shank has yet been established.
Thus, as a result of various experiments and research, the inventor devised to form at least the shank portion of the diamond tool which is in contact with a diamond chip using a reaction-sintered silicon carbide material. The tool produced according to this method has been confirmed to have better thermal resistance and effectively reduce vibrations during its use.
However, the thermal expansion coefficient of the diamond chip is not necessarily sufficiently close to that of thermal expansion of the shank portion formed of the reaction-sintered silicon carbide material. Consequently, in some cases stress attributed to the difference between the thermal expansion coefficients of the diamond chip and ceramics shank remains at the junction. This residual stress is responsible for cracks and exerts negative influence on the product yield and the life of products.